The present invention relates to a device for prevention of pollution in an aqueous medium.
More particularly, the present invention relates to a device for detecting certain organic pollutants, notably hydrocarbons, present in an aqueous medium.
In this field, there are well-known detection systems including at least one element sensitive to the pollutant which deteriorates or, more generally, whose mechanical properties change in contact with the pollutant.
The working principle of such detection systems, which is well-known, consists in making the sensitive element co-operate with means capable of activating an alarm when the sensitive element is deteriorated by the pollutant.
According to the applications considered, a sound or a visual alarm signal, or any other reaction means, may be activated as a result of the degradation of the sensitive element.
The degradation of the sensitive element may, for example, trigger off the scattering of an absorbing or a neutralizing product with respect to the pollutant.
Automatic detection devices sensitive to certain pollutants, notably hydrocarbons, and comprising two pieces of a band or of a wire glued together with a special glue which is deteriorated or dissolved by the pollutant, have already been proposed. The assembly being kept under stress, the action of the pollutant causes the assembly to break, which leads to the activating of an alarm signal. Such devices have, for example, been manufactured by the Canadian company Bennett Pollution Controls Ltd under the trade name "Oil Spill Detection System".
Such a system entails manufacturing difficulties and the results are little reliable as the sensitivity of the gluing to the pollutants greatly depends on the manufacturing quality.
Other known devices are based on the use of a massive sensitive element which is caused to swell or is destroyed in contact with the pollutants, which leads to the activating of an alarm (see French patent No. 2,178,950).
Various products which have been proposed so far for making up the sensitive element are not completely satisfactory as they appear to be too little sensitive to pollutants (products according to French patent No. 2,178,950) or, when their sensitivity is sufficient, they do not withstand the action of light long enough (products according to French patent No. 2,254,749).
In order to remedy some of the drawbacks stated above, it has been proposed, in French patent FR-2,455,294 corresponding to U.S. Pat. No. 4,351,642, to use as a material deteriorating in contact with the products, a material comprising a butadiene-styrene sequential copolymer at least part of which is hydrogenated. Preferably, this material includes stabilizing agents with respect to ultraviolet rays, antioxidant agents and 400 k oil in proportions determined according to the use envisaged.
According to this embodiment, the sensitive element may be a thin band kept under traction and whose breaking, due to its deterioration by hydrocarbons, activates an alarm system.
It turned out that such a hydrocarbon detector is really active only in the presence of a certain amount of hydrocarbons in water. This detector acts above all as a fuse which is released only by the presence of large amounts of hydrocarbons.